It is a goal of this task to continually improve the conditions of the human and nonhuman tissues which have been cultured as explants. In addition, cultured explants are being exposed to chemical carcinogens in an attempt to induce morphological lesions as assessed by high resolution light microscopy and electron microscopy. NCI using the epon araldite embedding procedures, will supply up to 5200 blocks of human and rat bronchus and colon organ culture material. The contractor shall perform the following to achieve the above state goal. Stain the sections on slides with Toludine blue. Eastmen 910 is to be used as the mounting medium for coverslips. The contractor submitted block will consist of 3 sections/slide from each block, 1 slide per block with section thickness of one micron and block face dimensions to be a maximum of 0.4 x1.0 cm. This task will provide for a fixed unit price of $6.60 per block.